[Kshot3000]

Problem

SigmaByteReader.readBool() read a boolean as byte === 0x01:

readBool(): boolean {
  return this.readByte() === 0x01;
}

That is not what the reference implementation does. In sigmastate-interpreter, CoreDataSerializer.deserialize reads SBoolean as:

case SBoolean => r.getUByte() != 0

sigma-rust does the same (Literal::Boolean(r.get_u8()? != 0) in ergotree-ir/src/serialization/data.rs). So a boolean byte of 0x02, 0x80 or 0xff is true on the node and in sigma-rust, but Fleet parsed it as false — silently flipping the value of an SBool constant (in a box register, a context extension, or a tree constant) instead of reading what the reference reads. It was also inconsistent inside Fleet itself: readOption() already treats any non-zero byte as Some.

Canonical encodings are unaffected: writers (Fleet's included) only ever emit 0x00/0x01, and those read back exactly as before.

Fix

readBool() now returns this.readByte() !== 0, matching the reference. Changeset included (.changeset/tidy-bools-truthy.md, @fleet-sdk/serializer: patch).

One interaction worth flagging: at end-of-input on master, readByte() returns undefined, which this comparison would read as true rather than the old false. Neither is a real value — that axis is the out-of-bounds read fixed in #225, after which an EOF bool throws a RangeError before any comparison. This PR is deliberately scoped to the in-bounds value semantics.

Test evidence

Tests-first — both new tests fail on pristine master with exactly the predicted flip (expected false to be true for byte 0x02):

• sigmaByteReader.spec.ts: a bool is false only for 0x00; 0x01, 0x02, 0x7f, 0x80 and 0xff are all true.
• sigmaConstant.spec.ts: SConstant.from("0102") and SConstant.from("01ff") parse as true (controls "0100"/"0101" unchanged).

After the fix:

• Serializer suite: 375/375
• Full monorepo suite: 1134/1134 (66 files; master baseline 1132 + 2 new)
• Biome check on the changed files: clean

— Kyle Cox (@Kshot9000, https://x.com/kshot9000) · Support my Ergo work: 9fcM5RWnAjmP4vx5bnW6yohB6H9bLq8sJbaPLHtwZLtQPB32Pvy

[changeset-bot]

🦋 Changeset detected

Latest commit: 22b8dfb

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@fleet-sdk/serializer	Patch

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